This invention relates to a welding method which combines metal inert-gas arc welding (hereinafter referred to as "MIG welding") and laser welding.
MIG welding, as illustrated in FIG. 1, consists in generating an arc between a wire 1 and a substrate 3, with the site of welding shielded with an inert gas against possible oxidation, to melt the substrate 3 and the wire 1. The wire 1 is automatically fed to the shifting site of welding as the wire 1 gradually melts. During welding, the impulse of finely divided metal particles and the plasma stream cooperate to produce a penetration to depth P.sub.M.
Welding by laser beam, as illustrated in FIG. 2, effects welding of a given substrate 3 by focusing a laser beam 4 with a lens 5 to form a focal point near the surface of the substrate 3, with the flow of a shield gas directed to the site of welding, to melt the substrate 3 and produce a penetration to depth P.sub.L. When the substrate to be welded has a large thickness, the penetration at the site of welding must be given a proportionately increased depth. For the depth of this penetration to be increased solely by laser welding, the unit volume of the laser used is increased so much as to render the laser welding prohibitively expensive.